This disclosure pertains to method for fabricating high quality optical lenses by curing liquid PDMS droplets on a pre-heated smooth surface.
Lenses are traditionally constructed with rigid materials such as glass or plastics by mechanical polishing or injection molding. High optical quality lens surface requires well-controlled fabrication parameters which increases complexity and reduces yield. Current demands for complementary metal-oxide semiconductor (CMOS) image sensors have resulted in the increase in fabricating small lenses ranging from 1 mm to 1 cm in diameter. In addition, emerging applications of flexible optoelectronics demand mechanically flexible lens materials. Fluidic lenses in particular is a simple method of creating small lenses of high quality without the requirement of molds or complex parameter control. However, an encapsulated fluidic lens requires a system to provide mechanical stability, and prevent evaporation. In contrast, lens formation due to surface energy minimization during polymer curing has provided an alternative method for making high quality, low-cost “fluidic” lenses that are independent components, flexible and robust.
Polymers have been generally utilized as a lens material by three categories of fabrication techniques: 1) lithographic methods, 2) surface-tension-driven methods, and 3) imprinting or embossing methods. These approaches demonstrate the feasibility of creating lenses with good optical characteristics and reproducibility; however, these techniques involve either time-consuming fabrication procedures typically measured in hours, or have high costs due to lithographic or molding equipment required, and generally limit the size of the lens to the micrometer scale. A recently introduced alternative method of creating a lens by droplet formation requires iterative drop-bake cycles to achieve a desired focal length. What is needed is a method for the production of high quality, inexpensive lenses with optimal focal length that requires minimal steps and is low cost.